1. Field of the Invention
The invention relates to three-tube burners designed to produce a flame from a central injection and an annular peripheral injection of oxidizer and from an annular injection of fuel between the central injection and the annular peripheral injection of oxidizer, as well as to a method of injecting fuel and oxidizer by means of such a burner.
2. Description of the Related Art
Three-tube burners are used especially in glass furnaces, and can also be used in metallurgical furnaces, instead of two-tube burners for the purpose of being able to control the atmosphere in the furnace, to increase the momentum of the flame, to adjust the length of the latter according to the geometry of the furnace (for example in the case of narrow furnaces) and to modify its luminosity and, especially, its emission spectrum according to the type of material to be produced in the furnace, for example of the glass type.
At the present time, most oxygen burners used in glass furnaces are two-tube burners, the body of which is fitted with oxidizer supply devices and with fuel supply devices.
Replacing two-tube burners with three-tube burners for the purpose of achieving the abovementioned advantages is problematic since it then becomes necessary to manage three fluid streams, thereby increasing the overall size, and the number of supply ducts, and this means significant modifications have to be made to the plant intended to supply the burner with fluids.
The object of the invention is to remedy these drawbacks and for this purpose relates to a three-tube burner for a furnace, designed to be fastened to a furnace quarl in such a way that at least one end region of the burner is housed in the quarl in order to produce therein a flame projecting into the internal space of the furnace, the said burner being characterized in that it comprises an inlet for a fuel and a fuel feed tube connected to this fuel inlet, an inlet for an oxidizer and two oxidizer feed tubes connected to this oxidizer inlet, and a control valve for controlling the distribution of the oxidizer between the two oxidizer feed tubes.
By virtue of this arrangement, when replacing a two-tube burner with a three-tube burner the fluid supply plant can be reused as it is, without modification, and it is furthermore possible for the distribution of oxidizer between the two oxidizer feed tubes to be accurately adjusted.
The burner may also have one or more of the following characteristics:
one oxidizer feed tube and the fuel feed tube are housed in another oxidizer feed tube;
the feed tubes are arranged coaxially around one another, at least over part of their length;
the control valve is housed in the burner, by being inserted into an oxidizer feed tube;
the control valve is a plug valve;
it includes an oxidizer feed tube having an oxidizer inlet end open inside another oxidizer feed tube;
it comprises, coaxially arranged over at least part of their length, a central oxidizer feed tube, a fuel feed tube defining an annular space for flow of fuel around the central tube, an outer oxidizer feed tube defining an annular space for flow of oxidizer around the fuel feed tube, and an annular bush inserted into the annular space for flow of oxidizer between the fuel feed tube and the outer oxidizer feed tube, downstream of an open end of the central tube in the outer tube and also downstream of the inlet duct for the oxidizer, this bush having, on the one hand, a channel allowing the oxidizer to flow towards the quarl and, on the other hand, a movable member cooperating with the channel to form a control valve;
the bush has a channel in which a plug is housed, the said plug having a calibrated hole allowing the oxidizer to flow towards the quarl with a predetermined minimum flow rate;
the bush has a channel forming a valve plug in which a pivoting valve key is housed, the said key having a through-hole and able to move from a position in which the through-hole allows the oxidizer to flow with the maximum flow rate through the valve and thus with the minimum flow rate through the central tube to a position in which the through-hole prevents any flow of oxidizer through the valve and thus causes flow with the maximum flow rate through the central tube;
the valve includes an operating member allowing it to pivot manually;
the valve includes a driving member designed to be connected to a motor-drive device.
The invention also relates to a method of injecting fuel and oxidizer into a furnace quarl by means of a burner for producing a flame projecting into the internal space of the furnace, characterized in that an oxidizer is introduced into the burner via a first inlet and a fuel is introduced via a second inlet, the fuel coming from the first inlet flows towards the quarl through at least two oxidizer feed tubes mounted in parallel one with respect to the other, while the fuel coming from the second inlet flows towards the quarl through another fuel feed tube.
The process may furthermore have the following characteristics:
the distribution of the oxidizer between the oxidizing feed tubes is continuously adjusted;
the distribution of the oxidizer between the oxidizer feed tubes is adjusted manually;
the distribution of the oxidizer between the oxidizer feed tubes is adjusted in a motor-driven manner;
the distribution of the oxidizer between the oxidizer feed tubes is regulated or controlled; and
the fuel flows towards and is injected into the quarl in an annular manner around a first, central, stream of oxidizer and within a second, annular, stream of the same oxidizer.